database error while creating new group

Trying to view the group "Linux and Macos" casts an error:

Database errorThe DragonByte SEO database has encountered a problem.

MySQL Error : Got error 'empty (sub)expression' from regexp.

I know where that came from: while trying to create a group, I have a choice in leaving the group category empty, or use "uncategorized".
None of these options work. However, the new group id has been added to the table socialgroup, but the database has a prob with the regexp being empty.

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